Mold remediation is a serious subject, covered at large by professionals and institutions that specialize on the subject matter. While I'm not a mold expert, I do know air duct cleaning and how important it is to complete an HVAC Duct Cleaning after any mold, mildew, or fire restoration.
 
The HVAC system of a building, residential or commercial, is designed to convey the dirty undesirable air from the living space and replace it with clean, heated or cooled, conditioned air that is pleasant to breathe and comfortable to building occupants. Depending on the building type and room use, many building codes call for the air in a room to be exchanged five to 15 times per hour. For HVAC that are clean and have adequate filtration, every exchange of air generally means the indoor air quality is improving. However, when mold, mildew, soot, allergens, and other contaminants are present, in the HVAC system, the IAQ is reduced with every air exchange.
 
Proper source removal HVAC air duct cleaning, following any restoration project, will reduce the contaminants within the HVAC system and in some cases completely remove the chances of recontamination. It sometimes is overlooked that while a building itself is being remediated, the HVAC system is still in operation and therefore moving mold spores, smoke particles, and other contaminants throughout the return and supply air duct, as well as other HVAC system components. Because the HVAC system is redistributing the air throughout the building, a small about of dirty/contaminated air has the potential to recreate the need for an entire restoration project in as little as a few days.  
 
Source removal, the practice of cleaning by removing contaminants the HVAC system, is the method prescribed within the NADCA (National Air Duct Cleaners Assocaiton) Standard, ACR-2013. Source removal can be achieved in a variety of ways, but is most often achieved by using a negative air vacuum/collector, rotating duct brushes, and compressed air whips/skippers to loosen debris from the duct walls allowing the airflow from the vacuum/collector to evacuate it from the HVAC system. The methods for a proper professional HVAC Air Duct Cleaning have been continually developed and refined for 30 years by working professionals engaged with NADCA and other IAQ associations.
 
Want to know more? Check out "Industry Documents" at the bottom of this page for white papers, standards, and more information on duct cleaning.